It was Ford itself that found that the additives in oil really don't become very active until 1000 miles into the oil change. The oil filter should be fine past 3000 so long as your engine isn't a total shatpile.
Even when I had a standard oil filter, my UOA's at 5000 miles were better than good. I usually do 7000 now with my current dual Baldwin setup, and my UOAs are stupid good. As for that 15k stuff? I don't know. There are a few people on BITOG who have done 9-10k miles and gotten decent UOAs, but I honestly have never seen a UOA from a 15k oil change on a gasoline engine.
With my bypass filtration system, I should be able to do that without a sweat at all, but at that point, I worry more about the additive package thinning out than anything. You can certainly keep oil clean for 15k, but the additives package holding up? That's another story completely.